GI-XRD studies on surface structure of ultrafine Ti(C 0.5N 0.5)-WC-Ni cermets at high temperature

Abstract

Influence of coarse and ultrafine particle size of Ti(C 0.5N 0.5) on the high-temperature stability of various Ti(C 0.5N 0.5)-WC-Ni cermets under oxidizing atmosphere were compared. The evolved surface microstructure was correlated to the wear performance of the cermet exposed to similar thermophysical conditions. Investigation by glancing incidence X-ray diffraction revealed a considerable fraction of TiO 2, TiC and TiN in the near surface layer of the cermet heat treated at ∼873 K. Ultrafine cermets showed good high-temperature wear resistance, which was ascribed to the homogenous distribution of the ultrafine hard phase grains along with high total hard phase content of ∼82–85 vol.%. Comparable wear performance in coarse cermets with 5 and 15 wt.% WC was also observed in spite of a low total hard phase content (66–72 vol.%), which was attributed to the high TiN in the surface. The presence of high amount of NiO (∼22 vol.%) and low Ni in the surface layer of WC-rich (25 wt.%) coarse grade cermet contributed to its poor high-temperature wear resistance